1. Field of the Invention
The present invention relates to electromagnetic valve units, and more particularly to an improvement of an electromagnetic valve unit which includes a flow control valve assembly for controlling the flow of fluid passing therethrough and an electromagnetic motor assembly for actuating the valve assembly in accordance with an electric current applied thereto from an electric power source.
2. Description of the Prior Art
In such a conventional motor assembly as described above, a stationary core and a movable core are coaxially arranged with respect to each other and surrounded by a solenoid coil within a motor housing. The movable core is also arranged between the stationary core and a yoke member to be axially moved by linear attraction force acting thereon in accordance with an electric current applied to the solenoid coil from the electric power source. In operation of the motor assembly of this type, when the solenoid coil is energized by a constant current from the electric power source, linear attraction force acting on the movable core changes in accordance with axial movement of the movable core. It is, therefore, difficult to conduct axial movement of the movable core in proportion to a value of the electric current applied to the solenoid coil.
Furthermore, in such a conventional valve unit as described above, a valve element of the valve assembly is secured to one end of a shaft integral with the movable core or directly secured to the movable core. As a result of the arrangement of the valve element related to the moveable core, it is difficult to ensure concentricity of the yoke member and the movable core within the motor housing and of a valve seat cooperating with the valve element within the valve housing. This hinders axial movement of the movable core and operation of the valve assembly.